Study On Extraction And Insecticidal Activity Of Bioactive Components In Meliaceae Plants

Those Meliaceae plants are promising to be developed as pesticide,owning to the advantages of effectively killing injurants instead of non-target critters,being easy to decompose without polluting environment.To develop the inartifical ecotypic pesticides, the dissertation focuses on the research of extraction and separation of the bioactive components in Meliaceae plants.Meanwhile,biological activity to wheat aphids was studied in this paper.The procedure of spectrophotometry analysis of saponins in Meliaceae plants was investigated in this paper.By comparison,the highest content of saponins in the bark of Melia toosendan Sieb.et Zucc.is about 36.3 mg/g.Different methods including traditional water extraction,thermal refluxing extraction,microwave extraction and ultrasonic wave extraction were employed to extract saponins from the the bark of Melia toosendan Sieb.et Zucc.Through the single-factor and orthogonal experiment,the optimum condition for extraction by ethanol was determined:ratio of solid to liquid was 1:10,extraction time was 4 h,concentrations of ethanol was 80%,extraction temperature was 75℃.The saponins in the bark of Melia toosendan Sieb.et Zucc.was purified with chromatographic column packed with KD-1 macroporous absorption resin.Through the single-factor and orthogonal experiment,the optimum condition for microwave extraction by ethanol was determined:ratio of solid to liquid was 1:30, extraction time was 10 min,concentrations of ethanol was 70%,extraction power was 595 W.By extraction with chloroform and purification with re-crystallizing technique,a white needle crystal was obtained.The two green spots of TLC were fairly clear,which were the isomers of toosendanin.The purity of Toosendanin is 98.63%,which was determined by thin-layer chromatology and high performance liquid chromatography(HPLC).The analyzing results by RP-HPLC showed that the recovery rate was 98.87%and RSD was 0.94%.It indicated that this technique is reliable in determining the content of toosendanin and the precision is as high as the veracity.This dissertation focuses on the biological activity of the extracts from the bark of Melia toosendan Sieb.et Zucc.,saponins from Melia toosendan Sieb.et Zucc.,saponins from Toona sinensis and toosendanin.In a laboratory study the four extracts also possessed stomach toxicity,contact and anti-feeding activity to wheat aphids.But the stomach toxicity and anti-feeding activity is better than contact activity.Toxicity curves of the extracts from the bark of Melia toosendan Sieb.et Zucc.to wheat aphids was y=1.2318+1.3921x,LC₅₀ was 509.1 mg/L after 48 hours.Toxicity curves of saponins in Melia toosendan Sieb.et Zucc.to wheat aphids was y=2.9150+1.1576x,LC₅₀ was 63.26 mg/L after 48 hours. Toxicity curves of saponins in Toona sinensis to wheat aphids was y=1.6946+1.6539x,LC₅₀ was 99.11 mg/L after 48 hours.Toxicity curves of toosendanin to wheat aphids was y=4.3044+1.5851x,LC₅₀ was 2.75 mg/L after 48 hours.The insecticidal activity sequence is Toosendanin＞Saponins in Melia toosendan Sieb.et Zucc.＞Saponins in Toona sinensis＞the extracts from the bark of Melia toosendan Sieb.et Zucc.